jQuery/CSS - Password strength meter using zxcvbn.js and backspace

When I type in a password, it seems to work correctly, i.e. the meter grows and changes color appropriately for the password strength as determined by zxcvbn. The problem comes when backspacing - deleting characters from the password. It, too, works initially, until I reach the last one or two characters. At that point, the meter stops decreasing and remains partially visible, the equivalent of perhaps a password strength of 10%, even when the percentage strength is 0. (For verification, there is a console.log statement that outputs the current password strength percentage to the console.)

So, there is either something wrong with the way I am determining the value in the password input control or there is some quirk or different way I need to handle the key-up event, whether in general or specifically when the key that is involved is the backspace key (delete key on my Mac).